The IgE-binding regions of the major allergen pen a 1: Multiple epitopes or intramolecular cross-reactivity?

The muscle protein tropomyosin is the major allergen (Pen a 1) in brown shrimp, Penaeus aztecus, lobster, crab, mollusks and other invertebrates such as house dust mite, and cockroach. Pen a 1 contains five major IgE-binding regions, and sequences that are rarely or never recognized by IgE antibodies from shrimp-allergic subjects. The molecular structure of tropomyosins is simple and repetitive; it is made up of multiple heptad repeats. The analysis of sequence identities and similarities of major, minor and non-IgE-binding regions indicate that intramolecular cross-reactivity to the multiple IgE-binding regions of Pen a 1 is not due to repetitive, identical or similar, cross-reacting sequences but due to multiple, independent epitopes. However, an allergenic motif may explain the reactivities to the five identified major IgE-binding regions.